This isn't going to work too well. You can't just mix and match operations from two separate processes (lost wax and sand casting) and expect good results. You might be able to use your original gear as a sand-casting pattern, but it won't work well because of the sand texture in the teeth. It would still need machining to function well. Don't try pouring molten aluminum on a wax part buried in a mold - it can volatilize the wax rapidly and blow the metal back into your face. And if you try burning out your oil-bonded sand mold, it will just collapse into a heap. Plus, burning teflon is toxic.
Even if this all did work okay (unlikely) the shrinkage of the wax plus the metal will make it too small. You could probably duplicate these gears just fine by pouring a 2-part plastic (Alumilite?) into your mold. And in the meantime, you can find someone who knows how to do casting (sand or lost wax) and have him/her show you how to do it safely and effectively.
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